This invention relates to fluorine-generating electrolytic cells.
The production of fluorine by the electrolysis of a fused electrolyte containing potassium fluoride and hydrogen fluoride is well known. During electrolysis heat is generated and the electrolyte must be cooled. The cooling of the electrolyte has been achieved by the provision of cooling tubes immersed in the electrolyte. In one form of cell used for the large scale production of fluorine the electrolyte is cooled by cooling coils. A cell of this kind is hereinafter referred to as being a fluorine-generating electrolytic cell of the kind specified. In such a cell, the cooling coils may also act as cathodes. The cooling coils can be mild steel.
Hitherto, cells of the kind specified have been operated with a water-cooled base so that a layer of "frozen" electrolyte is formed on the base so as to electrically insulate the base and hence prevent the generation of hydrogen at the cell base, this generation being undesirable since the hydrogen could otherwise migrate to the anode compartments of the cell where it could interact with fluorine with potentially serious consequences.
British Patent Specification GB-A-2135334 discloses an alternative approach in which, instead of insulating the cell by means of a solid layer of electrolyte, a polymeric material such as polytetrafluoroethylene is applied to the cell base. The polymeric layer need only be of the order of 2 mm thick (in contrast with a solid electrolyte layer typically of the order of 50 mm thick) with the advantage that the anodes can be made longer.
The present invention addresses the problem of securing the insulating layer to the cell base without adversely affecting the integrity of the cell base.